In the oil industry, for example, choke valves are used to control or throttle fluid flows from oil or gas fields whereby to maintain a substantially constant flow rate irrespective of pressure fluctuations in the flow line. The fluid flow can be a mixture of oil, gas and solid particles, such as sand, and such a multi-phase flow provides an extremely harsh and abrasive medium for conventional choke valves which rely on movable components to control flow.
The aim of the invention is to provide a control arrangement which does not utilise a conventional valve but rather relies upon a fluidic device known as a vortex amplifier which does not have moving parts and seals which suffer wear and corrosion during use. A vortex amplifier comprises a vortex chamber through which a main flow passes radially to emerge at an axial outlet. The main flow can be regulated and controlled by a control flow introduced tangentially into the vortex chamber.